Normal aging in humans is recognized as producing some or all of the following typical physiological results:
1. Brain weight is reduced by 15%
2. Blood flow to the brain is reduced by 20%
3. Body water content is reduced by 18%
4. Body weight is reduced by 12%
5. Nerve conduction velocity is reduced by 10%
6. Number of nerve fibers in nerves are reduced by 37%
7. Decreased amounts of enzymes and coenzymes
8. Decreased amounts of neurotransmitters
9. Depletion of oxidative, phosphorelative enzymes
10. Apoptosis—chronic neuronal atrophy
In describing their work in an article entitled “Studies on Age-Dependent Ozonide Changes in Human Cerebral Cortex,” (by Reichlmeier K., Ermini M., and Schlecht H. P.—Aktuelle Gerontol 1978 August 8(8):44-8), the authors report that they investigated the activity of various enzymes of human brains obtained at autopsy and covering an age range of 19 to 91 years. Protein kinase, which mediates the information carried by the second messenger, cyclic AMP (3′, 5′-cyclic adenosine monophosphate), does not show age-related changes of basal activity. Cyclic AMP-dependent activation of protein kinase remains nearly constant up to 60 years of life, but it undergoes a distinct and progressive decline between 60 and 90 years. In the corpus striatum, no age related changes of cyclic AMP-dependent protein kinase activity were observed. The activity of carbonic anhydrase exhibits, in both human cortex and corpus striatum, an age-dependent decrease that also begins after the sixth decade of life.